Remove unused variable Game::sfpsmode

This variable does absolutely nothing, so I'm removing it.

desktop_version/src/Game.cpp

@@ -268,7 +268,6 @@ void Game::init(void)
     hardestroomdeaths = 0;
     currentroomdeaths=0;
 
-    sfpsmode = false; //by default, play at 30 fps
     inertia = 1.1f;
     swnmode = false;
     swntimer = 0;